1. Field of the Invention
The present invention relates to a magnetic head being suitable for a video cassette recorder, a video tape recorder, a magnetic disk apparatus, or the like and, more particularly, to a magnetic head having a coil which is formed by a thinfilm process.
2. Description of the Related Art
As a magnetic head used in a magnetic recording/reproducing apparatus such as a video cassette recorder, a video tape recorder, or a magnetic disk apparatus, a metalingap (MIG) type magnetic head in which a magnetic metal film is formed on a magnetic gap forming surface of a magnetic core consisting of ferrite or a socalled laminate type magnetic head in which a magnetic metal film is sandwiched by a pair of nonmagnetic ceramic substrates, and the like are in practical use.
The magnetic head copes with improvement on image quality or progressing of digitalization. For this reason, the magnetic head must exhibit preferable electromagnetic conversion characteristics in a highfrequency band to obtain highdensity recording performance. However, the MIG type magnetic head is not preferably used in a highfrequency band because its high impedance. In the laminate type magnetic head, a magnetic metal film constituting a magnetic path must be decreased in thickness when a track width is reduced for highdensity recording, and, therefore, reproducing efficiency is degraded.
As in a helicalscantype magnetic recording/reproducing apparatus, in a magnetic recording/reproducing apparatus in which a recording/reproducing operation is performed while a magnetic head is rotated, the magnetic head is mounted on a rotating drum. At this time, in a MIG type magnetic head or a laminate type magnetic head, a magnetic head is adhered to a terminal plate, and the terminal plate is fixed to a rotating drum, thereby mounting the magnetic head on the rotating drum. Here, the terminal plate includes a terminal corresponding to a lead line extending from a coil wound on the magnetic core of the magnetic head. The coil wound on the magnetic core and an external circuit are rendered conductive to each other through the terminal plate.
In a magnetic recording/reproducing apparatus in which a magnetic head is mounted on a rotating drum as described above, in order to increase a data transfer rate, a large number of magnetic heads are desirably mounted on a small rotating drum.
However, a terminal plate generally has a large size. For this reason, according to the method in which a magnetic head is adhered to a terminal plate and fixed thereto, and the magnetic head is mounted on a rotating drum as described above, a large number of magnetic heads cannot be easily mounted on a small rotating drum. More specifically, since an MIG type magnetic head or a laminate type magnetic head requires a terminal plate when the head is mounted on the rotating drum, the magnetic heads mounted on the rotating drum are limited in number.
As a magnetic head which solves the problem on the MIG type magnetic head or the laminate type magnetic head described above and copes with a highfrequency band, for example, as described in Japanese Unexamined Patent Publication No. 63231713, a magnetic head (to be referred to as a bulk thinfilm head hereinafter) in which a magnetic path constituted by a magnetic metal layer is made small, and a coil for driving a magnetic head is formed by using a thinfilm process is proposed.
As shown in FIG. 1, a bulk thinfilm head 100 includes a magnetic head halfmember 103a in which a magnetic metal layer 102a serving as a magnetic core is formed on a part on a nonmagnetic substrate 101a and, similarly, a magnetic head halfmember 103b in which a magnetic metal layer 102b serving as a magnetic core is formed on a part on a nonmagnetic substrate 101b. One pair of magnetic head halfmembers 103a and 103b are joined to each other such that the magnetic metal layer 102a of one magnetic head halfmember 103a opposes the magnetic metal layer 102b of the magnetic head halfmember 103b through a magnetic gap g1.
In the bulk thinfilm head 100, thinfilm coils are buried into one pair of magnetic head halfmembers 103a and 103b to be wound on the magnetic metal layers 102a and 102b. External connection terminals 104a and 104b extending from the thinfilm coils are formed to be exposed on the side surface of the bulk thinfilm head 100.
In the bulk thinfilm head, in addition to excellent characteristics in a highfrequency band, the coils for driving the magnetic head are buried in the magnetic head halfmembers serving as the thinfilm coils. For this reason, the magnetic head can be directly mounted on the rotating drum without using a terminal plate. More specifically, in the bulk thinfilm head, the coil for driving the magnetic head is constituted by the thinfilm coil buried in the magnetic head, and the terminal extending from the thinfilm coil is formed to be exposed outside the magnetic head. For this reason, the magnetic head can be mounted on the rotating drum without using a terminal plate. Therefore, in the bulk thinfilm head, a large number of magnetic heads can be mounted on a small rotating drum.
In a conventional MIG type magnetic head or a conventional laminate type magnetic head, when a magnetic head is adhered to a terminal plate and fixed thereto, the left and right winding guide grooves for winding a coil for driving the magnetic head are made different from each other to prevent the magnetic head from being erroneously adhered to the adhering surface of the terminal plate.
More specifically, for example, as shown in FIG. 2 which shows an example of the MIG type magnetic head, the width of a winding guide groove 111a formed in one magnetic core 110a is increased, and the width of a winding guide groove 111b formed in the other magnetic core 110b is decreased. In this manner, a leading core serving as a magnetic core on the side on which a magnetic recording medium advances during a recording/reproducing operation can be discriminated from a trailing core serving as the other magnetic core.
In contrast to this, in a bulk thinfilm head, since a thinfilm head serving as a coil for driving a magnetic head is used, no winding guide groove is required. Therefore, in the bulk thinfilm head, the shape of the leading core and the shape of the trailing core are symmetrical. For this reason, in the bulk thinfilm head, it is disadvantageously difficult to discriminate the leading core from the trailing core.
In the MIG type magnetic head or the laminate type magnetic head, when the color or the like of the terminal plate is changed, different types of magnetic heads, i.e., magnetic heads respectively having different azimuths, can be discriminated from each other.
On the other hand, a large number of magnetic heads can be mounted on a small rotating drum without using terminal plates. However, when the magnetic heads are to be directly mounted on the rotating drum without using terminal plates, the types of the magnetic heads cannot be discriminated from each other depending on the colors or the like of terminal plates.